Can't unlock PAYG Iphone 11 Pro Max

[Potter55]

I am trying to get an unlock code for my Iphone 11 pro max, I have used it on Vodafone PAYG for 3 months and wish to use a different network. I asked for an unlocking code but they say I can't have one as I didn't buy the phone from Vodafone so have to go to original purchase place. It is a second hand phone so no idea where I was originally bought. How can this be fixed as I need it unlocking 

[BandOfBrothers]

Have you tried an alternative activated network sim card as iPhones are typically already unlocked @Potter55 

There are Highstreet Stores that advertise they unlock iPhones for a fee as well as some reputable online companies.

Edited to add > " Unfortunately, we can't unlock your device if you didn't buy it directly from us, for example, from Carphone Warehouse "